The present invention relates to a wiring board having a wiring board main body and its manufacturing method, and more particularly to a wiring board and its manufacturing method that can reduce a warp of a wiring board main body and make smaller the size of the wiring board in the thickness direction.
Conventionally, there is a wiring board called a coreless substrate in which the size of the wiring board in the thickness direction is made smaller. Since the coreless substrate does not have a core substrate, the strength is lower and the warp is more likely to occur than a build-up wiring board with a core substrate (wiring board formed with a build-up structure on both surfaces of the core substrate). There is a wiring board 200 as shown in FIG. 1 in which the warp of the coreless substrate can be reduced.
FIG. 1 is a cross-sectional view of the conventional wiring board.
Referring to FIG. 1, the conventional wiring board 200 has a wiring board main body 201 that is a coreless substrate and a stiffener 202. The wiring board main body 201 has an electronic component attaching pad 211, the dielectric layers 212 and 216, the via holes 213 and 217, a wiring pattern 215, an external connection pad 219, and a solder resist layer 221.
The electronic component attaching pad 211 has a connection surface 211A with which an electronic component 204 (e.g., semiconductor chip) is connected. The electronic component attaching pad 211 is disposed inside a dielectric layer 212 so that the connection surface 211A may be almost flush with a surface 212A of the dielectric layer 212 (surface of the dielectric layer 212 on the side where the stiffener 202 is disposed).
The dielectric layer 212 has an opening portion 225 for exposing a part of a surface 211B of the electronic component attaching pad 211 located on the opposite side of the connection surface 211A. A via hole 213 is provided in the opening portion 225. One end portion of the via hole 213 is connected with the electronic component attaching pad 211.
The wiring pattern 215 has a pad 227 and a wiring 228. The pad 227 is provided on the surface 212B of the dielectric layer 212 located on the opposite side of the surface 212A. The pad 227 is integrated with the wiring 228. The pad 227 is electrically connected via the wiring 228 with the electronic component attaching pad 211.
The wiring 228 is provided at the other end portion of the via hole 213 and on the surface 212B of the dielectric layer 212. The wiring 228 is integrated with the via hole 213 and the pad 227, as well as being connected with the electronic component attaching pad 211 and the pad 227.
The dielectric layer 216 is provided on the surface 212B of the dielectric layer 212 to cover the wiring 228. The dielectric layer 216 has an opening portion 231 for exposing a part of the pad 227. The via hole 217 is provided in the opening portion 231. One end portion of the via hole 217 is connected with the pad 227.
The external connection pad 219 is provided at the other end portion of the via hole 217 and on a surface 216A of the dielectric layer 216 (surface of the dielectric layer 216 on the opposite side of the surface in contact with the dielectric layer 212). The external connection pad 219 is integrated with the via hole 217. The external connection pad 219 has a connection surface 219A on which an external connection terminal (not shown) is disposed. The external connection pad 219 is electrically connected via the external connection terminal (not shown) disposed on the connection surface 219A with a packaging board (not shown) such as a mother board.
The solder resist layer 221 is provided on the surface 216A (surface of the dielectric layer 216 on the opposite side of the surface in contact with the dielectric layer 212) of the dielectric layer 216 to cover the connection surface 219A. The solder resist layer 221 has an opening portion 221A for exposing the connection surface 219A.
The stiffener 202 is a framework in the shape of a frame, and has a through portion 202A for receiving the electronic component 204 (exposing an area where the electronic component attaching pad 211 is formed). The stiffener 202 is bonded with the surface 212A of the dielectric layer 212 with a resin (e.g., epoxy resin) having adhesiveness. The stiffener 202 is formed by etching or punching a Cu plate or Cu alloy plate, for example. The thickness of the stiffener 202 may be 2 mm, for example.
The warp of the wiring board main body 201 that is the coreless substrate can be reduced by providing the stiffener 202 with such a constitution on the wiring board main body 201.
FIGS. 2 to 5 are views showing a manufacturing process for the conventional wiring board. In FIGS. 2 to 5, the same or like parts are designated by the same reference numerals or signs as the conventional wiring board 200 shown in FIG. 1.
Referring to FIGS. 2 to 5, a manufacturing method for the conventional wiring board 200 will be described below. At first, in the process as shown in FIG. 2, the wiring board main body 201 is formed on an upper surface 235A of a carrier 235 having conductivity such as a Cu foil or Cu plate by a well-known method. Next, in the process as shown in FIG. 3, the carrier 235 provided on a structure as shown in FIG. 2 is removed. The carrier 235 is removed by wet etching, for example.
Next, in the process as shown in FIG. 4, the stiffener 202 is formed, and then the wiring board main body 201 and the stiffener 202 are disposed oppositely so that the dielectric layer 212 provided on the wiring board main body 201 and the stiffener 202 may be confronted. The stiffener 202 is formed by etching or punching the Cu plate or Cu alloy plate, for example. The thickness of the stiffener 202 may be 2 mm, for example.
Then, in the process as shown in FIG. 5, the stiffener 202 is bonded with the wiring board main body 201 by the resin 203 (e.g., epoxy resin) having adhesiveness. Thereby, the wiring board 200 is manufactured (e.g., refer to patent document 1).    [Patent document 1] JP-A-2000-323613
However, in the conventional wiring board 200, the warp of the wiring board main body 201 is reduced by providing the stiffener 202 on the wiring board main body 201 that is the coreless substrate. Therefore, there is a problem that the size of the wiring board 200 in the thickness direction is larger.